Polyisocyanurate foams have been used as a heat insulating layer in structural boards for applications such as fire doors, bulkheads and roofing boards for steel decks. In particular, steel deck roofs on structures such as shopping malls must be waterproof and insulated to conserve energy. The waterproofing and insulation must also be resistant to the spread of fire and should pass specifications such as the Class I designation of the Factory Mutual System of Norwood, Mass.
The polyisocyanurate polymer may be prepared by reacting a polyisocyanate, a polyol and other components such as an epoxide as set forth in U.S. Pat. Nos. 3,676,380, 3,799,896, 3,814,659, 3,909,346 and 3,940,517. As the reaction proceeds, applied heat causes the evaporation of an admixed blowing agent which results in the creation of the cellular framework of the foam.
However, prior polyisocyanurate processes and products have many disadvantages. For example, in some processes, the reaction mixture may require the application of a temperature of 150.degree. to 200.degree. F. which complicates the system and is wasteful of energy. Further, various processes necessarily require that the polyisocyanate be used in the form of its prepolymer reaction product with a diol. Additionally, some polyisocyanurate insulation boards, in order to pass safety standards, are required to be formed with web or sheet layers within the foam. Finally, reaction mixtures according to various prior procedures may be disadvantageous in that unacceptable amounts of reaction mixture must be discarded because the reaction fails to take place in the proper manner.
In view of the above, it is an object of the present invention to provide a polyisocyanurate process which requires the application of relatively low temperatures in order to promote the reaction and foam structure formation.
Another object of the invention is a polyisocyanurate foam insulating board with excellent structural integrity and precise dimensions.
A further object of the invention is a process for the production of a polyisocyanurate board where the board thickness may be maintained at an exact figure with consistent board density.